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The Effect of Yttrium on Oxygen Grain‐Boundary Transport in Polycrystalline Alumina Measured Using Ni Marker Particles
Author(s) -
Cheng Huikai,
Dillon Shen J.,
Caram Hugo S.,
Rickman Jeffrey M.,
Chan Helen M.,
Harmer Martin P.
Publication year - 2008
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2008.02391.x
Subject(s) - spinel , activation energy , crystallite , grain boundary , materials science , analytical chemistry (journal) , yttrium , oxygen , annealing (glass) , nickel , doping , grain size , mineralogy , aluminate , metallurgy , chemistry , microstructure , oxide , cement , optoelectronics , organic chemistry , chromatography
The grain‐boundary transport of oxygen in polycrystalline α‐Al 2 O 3 (undoped and 500 ppm Y 3+ ‐doped) was studied in the temperature regime of 1100°–1500°C by monitoring the oxidation of a fine, uniform dispersion of Ni marker particles (0.5 vol%). The annealing treatments were carried out in a high‐purity O 2 atmosphere (>99.5%). The Ni particles, which are visibly oxidized to nickel aluminate spinel, were used to determine the depth of oxygen penetration. The thickness of the reaction zone was measured as a function of heat‐treatment time and temperature, and a comparison of the oxidation rate constants and activation energies for undoped and Y 3+ ‐doped alumina was made. The results indicate that the presence of Y 3+ slows oxygen grain‐boundary transport in alumina by a variable factor of from 15 to 3 in the temperature regime of 1100°–1500°C. The values of the activation energy for undoped and Y 3+ ‐doped alumina were determined to be 430±40 and 497±8 kJ/mol, respectively.